Burglar alarm



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BY 9&5 cw mzw ATTORNEYS United States Patent BURGLAR ALARM Francis C. W. Stelter, New York, N.Y., assignor of onehalf to Richard C. Murphy, New York, N.Y.

Application January 31, 1957, Serial No. 637,552 2'Claims. (Cl. 340274) This invention relates to alarm devices and more particularly to devices of this type which are adapted to erably disguised as an innocuous article, where it would be visible to the publicin close proximity to the boundary wall or closure of an area which is to be safeguarded. This suspended body contains a sensitive electrical switching means which is adapted to close a circuit to an electrical alarm device upon tilting or jarring the body as a consequence of the vibration, or actual fracture or breakage of the wall or closure.

In its preferred adaptation, this body takes the form of a sign board of suitable size upon the rear surface of which is carried the switching device, the face of the sign adapted to be disposed in close proximity to the inner wall of the enclosure, as for example, the show window pane, or in actual contact therewith.

The sensitive switching device is preferably a mercury switch having one contact immersed in the liquid metal and the other in minutely spaced relation with respect to the surface thereof, whereby vibration of the device will cause the liquid metal to ripple and make contact with the spaced electrode. Similarly, if the device is given a swinging movement or tilted, as by actual breakage of the window, contact would be made by the dipping of one side of the electrode into the mercury, particularly if, as is contemplated, the electrode is of considerable horizontal width.

Other objects and features of novelty will be apparent from the following specification when read in connection with the accompanying drawings in which certain embodiments of the invention are illustrated by way of example.

In the drawings:

Figure l is a somewhat diagrammatic view in elevation showing the installation of an alarm device, embodying the principles of the invention, behind a display window;

Figure 2 is a rear view of the alarm device with a portion of the housing of the contactor shown in section for clearness of illustration;

Figure 3 is a fragmentary horizontal sectional view taken on line 33 of Figure 2;

Figure 4 is a vertical sectional view taken substantially on line 4-4 of Figure 3 and showing how vibration of the liquid surface will make contact to set off the alarm;

Figure 4A is a similar view showing the contactor in tilted position and also making contact with the liquid surface; and

Figure 5 is a diagrammatic view in vertical section of a modified form of contact vessel or container.

In Figure 1 of the drawings the plate glass pane of an enclosure such as a store window is indicated at 10 and the novel alarm device 12 is suspended immediately rearwardly of the pane 10 and preferably in actual contact therewith by means of the conductor cable 13 which may pass over a pulley 14 in the upper portion of the store window whereby the device may be raised and lowered as desired.

As will be noted, the front face of the body 12 is in the form of a sign which may be made of metal or any other suitable material and, if desired, may be of the type widely used to indicate the identity of the protective organization engaged by the proprietor of the store in which the installation is made.

Referring now'to Figure 2 of the drawings, it will be seen that there is secured to the back face of the sign 12 a housing 15 which may be made of sheet metal and se cured to the sign as by means of the screws or other closure 23 such as the screw cap shown in the drawings is applied to the top of the container 20 and has an internally threaded bushing 25 fitted securely in a central opening therein. The bushing 25 may be provided with a peripheral groove 26 within which one end of a conductor 27 may be secured.

Threaded within the plug or bushing 25 is a tubular member 30 which is made of conducting material and is provided with a flaring fiat contacting foot portion 31 having the sloping top surface 32. The lower terminal portion 31 of the hollow tubular stem 30 is of considerable horizontal width and has a fiat under-surface as clearly shown in the drawings.

Passing downwardly through the tubular electrode 30 is the insulated conductor 35 which terminates, well beneath the minimum level of conducting liquid 21, in a metallic electrode 36 which of course makes contact with the body of fluid conductor 21.

The two leads or conductors 27 and 35 from the sensitive switch assembly may be conjoined to form the single cable 13 by means of which the device may be suspended. If desired, in order to normally maintain the sign 12 in horizontal position the conductors 27 and 35 may be brought laterally outwardly and passed around the fastening elements 38 and thence converging upwardly to the joint conductor 13.

As diagrammatically shown in the upper right-hand portion of Figure 1 the separate cables 27 and 35 are continued into the alarm circuit where the wire 27 leads to a manuallyv operable switch 40 and thence to a source of current indicated diagrammatically as a battery 41. The circuit is completed from the battery to an alarm device such as the bell 44 and thence to the return conductor 35.

The operation of the alarm device will be readily apparent. When the suspended element 12 is to go into operation, the suspending cable 13 is lowered over the pulley 14 and the element 12 brought into close proximity or actual contact with the window pane 10. The manual 0n and Off switch 40 is closed. Previously, the terminal 31 of the hollow electrode 30 has been adjusted a very slight distance above the upper surface of the mercury 21 by rotating the threaded electrode 30 in the bushing 25.

Then if the window is jarred or smashed, the vibration or tilting of the device 12 will either set up undulations in the surface of the conducting liquid 21 and thus make contact with the electrode base 31 and set ofi the alarm or if the device 12 is tilted or set in swinging oscillation, the angling of the device will cause one portion of the circular periphery of the electrode base 31 to contact or dip into the surface of the conducting liquid 21 as clearly shown in Figure 4A of the drawings. This will, of course, in like manner set off the alarm 44. The bell 44 is of course a generic showing for any sort of visual or audible alarm disposed at any point where the encroachment on the property should be brought to the attention of custodians or law ofiicers.

Within the broad scope of the invention, the sensitive body disposed in proximity to the window pane may be supported otherwise than by the suspension means illus- 1 trated; for example, the body in the form of the suggested sign or otherwise, may be set upon the How of the display space, supported by brackets from the window frame,

braced in position by a resilient easel or stand, or by any other suitable means for ensuring that the body will partake of the vibration, tilting or other movement sustained by the window upon the occurrence of tampering.

Also, except where specifically claimed, the invention contemplates the connection of the body of mercury or liquid conductor with one of the circuit leads by other means than the immersed electrode illustrated and de-- scribed. For example, as illustrated in Figure 5, the cup or vessel 50 containing the liquid conductor may be of metal and the container itself electrically interposed in the circuit. In the suggestive illustrated embodiment, the cover 51 of the cup or container 50 may be of insulating material and carry a threaded bushing 52 through which p a solid stem 53 may be adjustably passed, the stem described herein without departing from the-scope of the invention asdetermined by the subjoined claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. An alarm installation which comprises, in combination, a transparent frangible panel comprising part of the panel, two normally separated contacts carried by said body, a container carried by said body, a momening liquid in said container, one of said contacts 111 permanent electrical conducting relationship with said pool of liquid, the other of said contacts having a terminal portion spaced a minute distance upwardly from the surface of said pool of conducting liquid, whereby an undulatign of said surface or tilting of said container will cause the liqui to contact said terminal portion, conductors connecting said contacts with an alarm device and a source of current, whereby fracture of said frangible panel will set up appropriate swinging movement of said body to close the circuit through said contacts and set olf the alarm. a

2. An alarm installation which comprises, in combination, a glass panel comprising part of the enclosure of a window display or I the like, a contact-carrying body, means for camoufiaging said body to simulate a usual appendage of such adisplay, meansior suspending said body in such close proximity to said glass panel as to be jarred or swung in any horizontal direction upon fracture of said panel, two normally separated contacts carried by said body, a non-conducting container carried by said body, a pool of conducting liquid in said container, one of said contacts being directed downwardly and being permanently immersed in said pool of conducting liquid, the other of said contacts being tubular and encircling but insulated from said first mentioned contact, directed downwardly toward the surface of said pool of liquid, and having a terminal portion comprising a flat disc spaced a minute distance upwardly from the surface of said pool ofconducting liquid, whereby an undulation of said surface or tilting of the body in any direction whether parallel with or perpendicular to the glass panel, will cause the liquid to contact said terminal portion, conductors connecting said contacts with an alarm device and a source of current, whereby fracture of said glass panel will set up appropriate swinging movement of said body to close the circuit through said contacts and set off the alarm.

" References Cited in the file of this patent 1 UNITED STATES PATENTS 1,484,502 James Feb. 19, 1924 1,666,122 Denniston Apr. 17, 1928 1,754,360 Hendricks Apr. 15, 1930 l FOREIGN PATENTS 277,847 Switzerland Dec. 17, 1951 

